Tube-expanding device



Jan. 16, 1962 Filed DeG. 14, 1956 W. E. STARY TUBE-EXPANDING DEVICE 2Sheets-Sheet 1 1N VEN TOR.

Jan. 16, 1962 w. E. sTARY TUBE-EXPANDING DEVICE 2 Sheets-Sheet 2 FiledDec. 14, 1956 INVENTOR. www al@ f i States Filed Dec. 14, 1956. Ser. No.628,258 8 Claims. (Cl. 15382) This invention relates to improvements inthe rollertype tube-expanding tool. This tool is used to expand a linealportion of a metal tube by a rolling action to iiow the metal so as tothin the tube wall and diametrically enlarge the tube portion to bringit into tight engagement with the tube-hole in which it is beingassembled.

A principal use of this tube-expanding tool is vto make pressure-tighttube-joints between the ends of tubes and tube-sheets in heat-exchangeapparatus. A common form of such apparatus is .steam condensers used tocondense low-pressure steam to Convert said steam back to Water which isthen returned to the boilers. Many such condensers are quite large,having, at times, 30,000 to 40,090 tubes, with tubes less than l-inch0.1). and tube-sheets 1 to ll/z-inches thick. A considerable amount oftime is required to expandv such quantities of tubeends to assemble sucha condenser unit, and any irnprovements reducing the tube-expanding timeare valuable improvements in said art.

A type of tube-expanding tool commonly used for this Work is known as aself-feeding tool. Thisself-feeding tool is illustrated and described ina number of U.S. patents, such as the patent issued to Brackett, PatentNumber 2,448,512.

atct

This self-feeding type of tool normally has its rolls contained in aroll-cage with the outer edges of the rolislots being formed inward toform caging-lips, said caging-lips preventing the rolls from falling outof said roll-cage. The roll-cage and mandrel of the tool are free tomove, axially, relative to each other. A usual way to keep the mandrelfrom being pulled out of the roll-cage, or to keep said cage fromfalling ot` the end of the mandrel, is to have a retaining nutthreadably connected to the small end of the tapered mandrel, with saidnut being diametrically large enough so that it cannot pass though theroll-cage bore.

Thus the tool is a self-contained unit so that in its normal assembledcondition, the mandrel remains in the roll-cage and thus keeps the rollsin their caging slots.

A common working condition is that in which the longitudinal axes of thetubes are horizontal and the axis of the expanding tool is alsohorizontal. When the tool is to be used, `the roll-cage is slid forwardon the mandrel so that the rolls may radially retract to give theclearance needed toffreely insert the tool into the tube-end to beexpanded. The retaining-nut on the end of the mandrel prevents theroll-cage from being slid forward too far.

With the tool assembly in a horizontal plane, and with the rolls free toradially move in their slots, the rolls below centerline of the tool donot retract when the roll-cage is slid forward on the mandrel, and theserolls in the lower half of the assembly may remain at theradially-outward limit of their travel-range, as controlled by saidcaging-lips on the roll-slots.

The front end of these radially-extended rolls may catch on the end of atube into which the tool assembly is being inserted so as to push saidtube out of its proper longitudinal position, or the roll-cage may bepushed back on the mandrel thus expanding the rolls before the tool isproperly positioned in the selected tube-end.

A common method for holding the roll-cageforward, and the rolls in theirradially collapsed positions, while inserting the tool into a tube-endto be expanded, is that -in which lthe operator grips the roll-cage soas to hold said roll-cage forward on the mandrel and to hold the rollsin their radially-retracted positions while he gets the rolls startedinto the tube-end. Then he changes his grip so that the roll-cage can beslid forward into the `tube-end to the limit of its forward-travelposition as controlled by the stop-collar attached to said cage. Duringthis time, the cage is held forward on the mandrel so that the rolls mayremain loose inside their rollcage and inside the tube-end.

When the roll-cage portion of the tool is inserted into the tube-endwith the face of the stop-collar bearing against the face of thetube-sheet, or against the end of the tube, or both, thus establishingthe proper working position for the tool, the operator advances theimandrel into its working position by pushing on the driv= ing unitcommonly connected to the mandrel, thus initiatin g the tool Work-cycle.

Said driving unit provides the rotary power required t0 rotate themandrel so that when the mandrel is advanced sufciently to radiallyexpand the rolls into firm contact with the inner surface of the tubeportion to be expanded to thus give a firm frictional contact b etweenmandrel and rolls, the planetary action of the tool parts is producedwith the self-feeding action ofA the tool giving the additional mandreladvance movement with its associated radial expansion movement of vtherolls so that the rolling action of the tool producesV theV thinningofthe Wall of the tube-po`rtion being worked to enlarge saidtube-portion and bring it into tightengagement with its tube-hole. i.

It is obvious-that the required gripping of the `rollcage, and thechanging of the grip, associated with getting the tool into its properworking position, take time and thus slow down the tube-expandingoperation. Another factor involved which takes time and thus slows downthe cycle time when many tube-ends are being consecutively rolled andexpanded is that the frictional heat produced, when the tool works,heats the rolls and roll-cage so that it may become unpleasant orimpossible to grip the front portion of the-tool to guide the rollcageassembly into a tube-end because of this portion ot the tool becomingtoo hot. Lubricant is often applied into the tube-ends to reduce theheating eifects described above. This adds to the messiness of theoperation since a good portion of the lubricant is transferred to thetool parts and brought out of the expanded tube-end on the roll-cage.

A principal object of this invention is to provide a tube-expandingdevice in which the roll-cage portion of the tool is normally urgedforward relative to its mandrel with said relative axial movement beinglimited so that a mandrel, not having a retaining nut on its forwardend, is kept in the tool assembly thereby keeping the rolls of said toolin their roll-slots.

A further object of this invention is vto provide an assembly of theabove described character in which the axial force required, to obtainsaid improved results, is a nominal amount having substantially no eiecton the forces required to operate, and the controlling feel" developedin, the self-feeding tool assembly as hereto-` fore commonly used.

A further object of this invention is to provide a tool `assemblywherein all rolls are retained in Contact with the tool mandrel so thatwhen the mandrel is in its retracted position all rolls are alsoretracted, thus eliminating the need for caging-lips on the roll-slots,to keep the rolls from falling out of the tool assembly, and thuspermitting the tool to be freely inserted into a tube-end with no dangerof an extended roll catching on the tubeend.

Other objects will be described in the specification and claimssubmitted herewith.

The drawings illustrate a preferred forni of the invention withoutlimiting the improvements in their useful application to the particularconstruction and arrangements shown, which, for the purposes ofexplanation, have been made the subject of illustration.

In said drawings:

FIG. 1 is a side elevation of a tool assembly incorporating theimprovements of this invention, with said tool assembly connected to adriving unit which provides the work-producing power required by thetool.

FIG. 2 is a longitudinal sectional View of a tube-expanding toolconstructed to include the improvements of this invention, with the toolinserted into a tube-end to be expanded, and with the mandrel of saidtool assembly advanced to radially expand the rolls of said tool tobring said rolls into rm Contact with the inner surface of said tube-endto give the firm contact, between mandrel and rolls, required to producethe self-feeding tube-expanding action of the tool.

FIG. 3 is another longitudinal sectional view of the tool of FIG. 2 withthe mandrel additionally advanced and the tube-end expanded into itstube-hole.

FIG. 4 is a side elevation of the roll-cage portion of the above toolassembly with a part broken away to better show the roll-retainingfeature of this invention.

FIG. 5 is a transverse vertical section on the line 5 5 of FIG. 4,looking in the direction of the associated arrows.

FIG. 6 is a developed view of the peripheral surface of the portion ofthe roll-cage contained between the arrows associated with the line 6-6of FlG. 4, for a rollcage containing three rolls, with one of said threerolls removed from its roll-slot.

FIG. 7 shows an isometric view of one of the rol'- retaining springsshown in the developed view, FIG. 6.

FIG. 8 shows a side elevation of the roll-retaining spring of FIG. 7.

Referring to the drawings, 21 designates a power unit which may be usedto provide rotary power for driving the tool, 22 a portion of atube-sheet, and 23 a tube having an end positioned in its assemblyposition in a tubehole in tube-sheet 22.

The tube-expanding device comprises a tubular spring housing 24 withthreaded bore at its front end, with said threaded bore providing meansfor threadably connecting roll-cage 25 to said spring housing 24. Theseveral tapered rolls 26, confined in the conventional, tapered andangled, roll-slots in roll-cage 25, are sized proportionally to the wallthickness of the forward tubular portion of roll-cage 25 so that saidrolls 26 project beyond the cylindrical surface of the working-lengthportion of roll-cage 25 to make their contact with the inner surface oftube-end 23 while said rolls simultaneously project inward into thelongitudinal bore through roll-cage 25 to make their required workingcontact with tapered mandrel 27.

Tapered mandrel 27 connects to drive shaft 28 by any means suitable fortransmitting the rotating, pushing, and pulling forces applied on saidmandrel 27 by said drive shaft 28. The connection shown in the drawingsshows a mandrel having a tapered head 27h with said head 27h having adriving tang and with said drive shaft 28 having a socket to suit saidtapered head 27h with driving tang, and with the end of said drive shaft28 having an external thread on which may be assembled themandrelretaining nut 29.

The socket-end of said drive shaft 28 may be provided with across-drilled hole 28h suitably positioned to provide means forknocking-out head 27h of mandrel 27 by a conventional tapered drift-pin,with nut 29 being loosened or removed to permit such axial movement oftapered head 27h.

Drive shaft 28 is fitted with a bearing such as the double-acting thrustbearing shown, said bearing consisting of outer races 31a and 31h, innerrace 32, and the two series of annularly positioned balls confined intheir 4 f respective ball-cages, said ball and ball-cage assembliesbeing designated as 33a and 33b. Said double-acting thrust bearing isconfined in a fixed axial position on drive shaft 28 between theshoulder at the rear of the sockethead portion on drive shaft 28 and thefront face of sleeve 34 positioned in fixed engagement on the spindle ofdrive shaft 28 by means of pin 35 which connects sleeve 34 to driveshaft 28 through the suitably sized and positioned hole passing throughsaid two members.

The above described double-acting thrust bearing assembly serves thefollowing described functions in the device assembly. Inner race 32 isconnected, by the means shown and hereinbefore described, to drive shaft28 with said connecting means providing a connection having a minimumfrictional drag when drive shaft 28 rotates and inner race 32 remainsstationary. The external diameter of inner race 32 gives properclearance for a free-sliding lit in the bore of spring housing 24. Theexternal diameter of outer race Sla and ball and ballcage assembly 33ais less than the external diameter of inner race 32 to provide clearanceso that spring 36 freely clears said outer race 31a and ball-cageassembly 33a so that spring 35 bears against the surface of inner race32.

Spring 36 is a compression spring, one end bearing against the" face ofinner-race 32, and the other end bearing against the seat at the frontend of the springbore portion of spring housing 24. Thus spring 36normally urges drive shaft 28 back, tending to eject drive shaft 28 fromspring housing 24. Drive shaft 2S is confined inside spring housing 24by retaining ring 37 fitted in a suitable groove near the rear end ofthe bore of said spring housing 24.

Since roll-cage 25 is connected to spring housing 24, the spring 'actionwhich pushes back drive shaft 28 serves to retract tapered mandrel 27,connected to said drive shaft 28, relative to roll-cage 25 so that rolls26 of the expanding tool may be retracted. Similarly, retaining ring 37limits the axial movement of drive shaft 2S and thus limits the axialretracting movement of mandrel 27 so that mandrel 27 is not pulled outfrom between the several rolls 26 of the tool assembly. Thus the toolassembly, in its normal position, is a semi-solid assembly with mandrel27 retracted relative to roll-cage 25, so that rolls 26 may be radiallyretracted in their respective roll-slots, with said semi-solid assemblycondition being produced by the spring force, produced by spring 36,pushing inner race 32 into firm contact with retaining ring 37.

Drive shaft 28 may have a tapered shank, such as tapered shank 28s, forconnectingsaid drive shaft, and thus connecting said device, to thepower unit supplying the rotating force used to drive the tool.

The stop coilar which limits the depth roll-cage 25 may be inserted intoa tube-hole is the conventional anti-friction type permitting the thrustface of said collar to remain stationary while roll-cage 25 andconnected spring housing 24 rotate during the tube-expanding operation.

The stop collar may be as shown with thrust flange 24f being an integralpart of spring housing 24. Thrust sleeve 33 is connected to thrust ange243c through the annular series of balls 39 and retaining ring 40 togive a single-direction anti-friction thrust bearing with retaining ring40 being the keeper to hold the bearing parts in assembly.

It is often desirable to vary the projection of the rolls ahead of theface of the stop collar to thus select a desired length of thetube-joint to be expanded. This is accomplished in the form of thedevice illustrated by axially adjusting the position of the roll-cage 25relative to spring housing 24 by rotating the parts in their threadedconnection. As roll-cage 25 is advanced, or retracted, relative tospring housing 24, the projection of rolls 26, ahead of the face of stopcollar 38 is. increased or de- 'asias-i4 creased. 'Set screw 41 engagingin groove 25g locks the assembly of roll-cage 25 and spring housing 24to hold a selected axial position of these mating members.

As 4lierein'before described, a principal feature of this 'invention isthe means for holding the rolls inward against the mandrel of the tool,to thus keep said rolls lfrom falling out of the assembly andeliminating the need for caging-lips on the roll slots, and to alwayskeep the rolls in contact with the mandrel so that as said mandrel isretracted, said rolls radially retract. This is accomplished byroll-retaining springs 42, shown in detail -in FIGS. 4, 5, 6, 7 and 8.

The requirements for a spring to successfully retain the rolls are thatit have a good expansion range without being overstressed, that it exerta snliicient force on a -roll that it is retaining to lift said roll,against gravity, to thus retract said roll, and that it be of suchdesign that it does not take up too great a portion of the rolllength,for it is obvious that the length-portion on which said spring isworking must be outside the tube-joint being expanded and thus is anot-working portion of the `length of said rolls and their coniiningroll-cage.

Spring 42 accomplishes the above requirements by virture of its uniqueshape. Said spring 42 may be considered as being of three principalparts, the U-shaped n- 'ger Aportion 421, and the two support-legportions 42a and 4212. In operation, the end of finger 42]c bearsagainst thepsurface of roll 26 to push roll 26 inward Vtowardvthelongitudinal axis of the tool assembly. Thus finger 42j acts as acantilever spring and is subjected to bending stresses identical tothose in a cantilever beam loaded at one end. If all the deflection andstresses were taken in the finger (cantilever) portion of the spring,the spring would be overstressed and permanently deformed, or saidspring would soon break from fatigue failure resuliing from themagnitude of the stresses imposed on said spring.

rThis unique design transfers a considerable portion of the deflectionand stresses to torsional detiection and stresses in the legs 42a and42h. This is accomplished by forming said roll-retaining springs toprovide large-radius bends between the iinger and leg portions of saidsprings so that a considerable portion of the deflection and stressesimposed on said linger portion of a spring may be readily transmittedaround said gradually-curved bends and converted into said torsionaldetiections and stresses in said support-leg portions of aroll-retaining spring.

Curved support-legs 42a and 42h, freely confined in the annular cavitycontained between spring-groove :1, in roll-cage 25, and the innersurface of spring-retaining band 43, serve to anchor and support saidspring assembly against the cantilever-type loading applied on nger 42j,and to allow support-leg portions 42a and 42h to torsionally twist withsaid torsional deflection being a maximum at the point immediatelyadjacent to `finger 42j* portion of said spring, and with said torsionaldeflection fading out as the torsional reaction is absorbed by saidsupport-leg portions, 42a and 42h, of said spring assembly.

Thus bendingstresses in the cantilever beam, linger, portion 421, ofsaid roll-retaining spring are kept Within `safe limits to give spring42 a good service life.

The two side members of linger portion 42], of rollretaining spring 42,are of different length to thus put legs 42d and 42b in separateparallel planes, as shown in FIG. 8, to facilitate assembly. This givesan assembly as illustrated in FIG. 6, with leg 42a of one spring mem-Aber lying beside leg 4211 of an adjacent spring member, with said legmembers 42a and 42b being freely supported in the hereinbefore describedannu'ar spring cavity so that each support-leg member may separately actto absorb its share of the spring-loading reactions.

The maximum length for a 42a support-leg, as illus- VAtrated in PIG. 6,is the circular distance between 42j 6 linger portions of two adjacentroll-retaining springs 42. Obviously, for a spring with balancedstresses and deections in each side member of linger 42j, support-leg42b should be substantially the saine length` as leg 42a. Thecircumferential length of the support-legs portion of roll-retainingspring is the sum of the circular lengths of leg 42a and leg 42h plusthe width of linger 427. As shown in FIG. 6, the circumferential lengthfor the support-legs portion of a roll-retaining spring is limited to amaximum length of slightly less than two-thirds of the meancircumference of annular groove 25n, for the conventional three-rollexpanding tool. A support-legs portion of such circumferential length,for a roll-retaining spring 42, when-contined in said annular cavityformed by spring-groove 25u and spring-retaining band 43, gives amplecaging and support to develop the distribution of deliections andstresses in the finger and leg members as hereinbefore described.

Spring-retaining band 43 may be a press fit on the hub portion 25h, ofroll-cage 2,5, to thus remain in its assembly position confining thesupport-legs of the several spring units in their workingV positions.Said enlarged hub portion 25h, of cage 25, also serves to provide spacefor the radial movement of the finger portions of the severalroll-retaining springs so that the radial movement of rolls 26 is notrestricted by spring-retaining band 43.

A design feature of the roll-cage 25 contributing to the successfuloperation of this unique roll-retaining spring is the removal of thesharp corners between rol-slots and spring groove to provide clearancefor said gradually-curved bends between nger and support-leg portions ofspring [12. This is accomplished in the illustrated form of the deviceby the semi-circular cutouts through the tubular wall of the hub portionof roll-cage 25. Said semi-circular cutouts also facilitae the machiningof the roll-slots to provide a dat of sucient width at the rear end ofsaid roll-slots.

Mitering the corners between roll-slots and spring groove, in roll-cage25, to a depth equal to the depth of said spring groove, would serveequally well for providing adequate clearance for the bends betweenfinger and leg portions of the several roll-retaining springs 42.

Spring 36 is preferably of a design having a low springconstant value sothat said spring 36 has a maximum amount of deflection with a minimumchange in force, and spring 36 is preferably of a design applying anominal axial force between drive shaft 28 and spring housing 24. Theaxial force needed to keep roll-cage 25 forward relative to mandrel 27is usually a few pounds and the additional force required to obtainfull-stroke axial advancing of drive shaft 28 relative to spring housing24 may be on the order of one pound.

For example, a tool assembly for a S/s O.D., 16 gage, tube, having amaximum mandrel advance stroke of 2 inches is very satisfactory with a4-pound force imposed between drive shaft 23 and spring housing 24 whenmandrei 27 is fully retracted in roll-cage 25. Spring 36 used in thisassembly requires an additional one-pound of force to collapse saidspring 36 to give the full Z-inch advancing of mandrel 27 relative. toroll-cage 25. Thus the pushing force, applied by the operator, toadvance mandrel 27 -into working position is something less than 5pounds. Since said operator must exert a pushing force of some 50 poundsto get the required expansion of the tool, in a tube-end, to give arapid start to the self-feeding action, there is vno increased fatiguefactor involved in using this device. The axial component of theself-feeding force developed, which is the force drawing the mandrelforward to further expand the tool assembly as a tube-end is beingrolled and expanded, is several hundred pounds. Thus it is obvious thatthe very slight difference in opposing force, applied by spring 36, asthe self-feeding action of the tool occurs, is of no significance on theend result of the tube-expanding action. The variation of this opposingforce applied by spring 35 is a resultant of tli'e final axial-advanceposition of said mandrel 27 and is a variation in force of a smallfraction of one pound.

FIG. 1 shows the exterior surface of spring housing 24, and showsthereon the longitudinal knurl 245m. The longitudinal mark 24m, may besaid knurl, a group of one or more longitudinally scribed lines, or anyother type of marking which can be felt or seen by the operator usingsaid tool. Mark 24m may be used to give the oper ator a tactual orvisible indication of the number of turns made by said spring housing,and thus the number of turns of the connected roll-cage 25, therebygiving the operator an indication of the degree of the tube-expandingwork done, for those sets of conditions wherein the number ofrevolutions of said roll-cage, and the consequent expansion of saidrolls of said tool, may give an indication of the degree of expanding ofthe tube-end being expanded.

As hereinbefore described, the illustrations show a preferred form ofthe device. It will be apparent to those skilled in the art thatother'combinations of parts may be used to perform the tube-expandingoperation in this improved manner. Several such examples of othercombinations of parts are described in the following paragraphs.

The stop collar arrangements illustrated in applicants Patent Number2,772,716, issued December 4, 1956, may be used with this device. Suchan arrangement requires the threaded-shank portion of roll-cage 25 belengthened to provide a seat for the separate stop collar. Mandrel 27 ofsuch an assembly would be correspondingly lengthened. This arrangementpermits a greater adjustment of the penetration of the roll-cage into atube-end to be expanded.

A roll-cage of the types illustrated in FIG. 2 and FIG. 3 of the abovedescribed patent, Number 2,772,716, may be used with this device. Saidroll-cages have the outer edges of their roll-slots formed inward toprovide caginglips to retain the rolls in said roll-cages, thuseliminating the need for roll-retaining springs 42. This combination maybe used in applications where a long and pointed form may be used on thefront end of rolls 26. The long, pointed, form gives a roll assemblywith ends of rolls concealed inside the periphery of roll-cage 2S sothat said roll-ends cannot catch on the end of a tube in which the toolis being entered, and so that any of said rolls which may be in aradially-extended position, in their rollslots, such as the rolls belowthe horizontal centerline of said roll-cage, may be radially floatedinward as said tool is entered into a tube-end to be expanded. Such anassembly has the improvement of the roll-cage remaining forward,relative to the mandrel of said assembly, without the operator needingto use one hand to hold said rollcage forward to permit said rolls insaid roll-cage to be in their radially retracted positions.

An alternate method of confining the roll-retaining springs in position,with their support-leg portions freely contained in groove 2511, inroll-cage 25, is to use a short length of a closely-coiled wire springmember, being in effect a tube similar to band 43, but by virtue of itsbeing a coiled spring which may be twisted, with said twist tending tounwind said coil, so as to open up the LD. of said coil, to thus providea band having an adjustable LD. A short tab, extending forward on thefront end of said coil, formed by bending the end of the wire normal tothe lay of said coil and in the plane of the cylinder formed by saidcoil, may be used as a convenient means lfor gripping said coil tothereby apply said untwisting force.

Said coil-spring type of band eliminates the need for close-limittolerances on `the 0.1). of hub 25h, of roll-cage 2S, and in the I.D. ofbmd 43, such as are required if band 43 is a metal tube and is to be apress lit on said hub 25h.

While the invention has been described with reference to theparticolari,` devices illustrated, itis to be appreciated that it is notso limited. It is rather of a scope commensurate with the scope of thesub-joined claims. K

What l claim as my invention is:

1. A. device for expanding a tube-end into its tubehole, by means of aroller-type tube-expanding tool having a tapered mandrel, a plurality ofexpanding rolls, and a tubular roll-cage with roll slots formed therein,with said expanding rolls and said roll cage mounted about said mandrelso that said rolls are radially movable in the roll slots in said rollcage and rotatable in and with said roll cage, about said mandrel;comprising a tubular spring housing cooperatively connected to a driveshaft so as to permit relative rotatable and axial movement between saidspring housing and said drive shaft, with said relative axial movementbeing limited by said connecting means, with a spring housed in saidspring housing so as to be freely rotatable with said spring housing,relative to said drive shaft, said spring normally urging said springhousing axially forward, relative to said drive shaft, to the forwardlimit of said relative axial movement between said spring housing andsaid drive shaft, wherein means are provided for connecting said rollcage to said spring housing, and means are provided for connecting saidtapered mandrel to said drive shaft.

2. A device as in claim l; wherein at least some of said roll slots areangularly cocked so that said expanding rolls contained in saidangularly-cocked roll slots are cocked to effect a self-feeding actionof said mandrel.

3. A device as in claim 1; wherein a plurality of rollretaining springsare cooperatively connected to said roll cage, said roll-retainingsprings acting to radially retain said expanding rolls in said too-lassembly, each of said roll-retaining springs being a formed wire havinga U-shaped linger connected to two support legs, said inger being formedto lay on one of said rolls in said roll cage, said finger projectingangularly from the plane of said support legs, an annular cavity in saidroll cage, said annular cavity comprising an annular groove in theperiphery of said roll cage circumscribed by a band supported by theperipheral surface of said roll cage adjacent to said annular groove,said annular cavity being positioned in the shank portion of said rollcage to thereby be positioned outside the working-length portion of saidroll cage, said support legs, of said roll-retaining springs, beingformed to lay in said annular cavity in said roll cage, the overallcircular length of the support legs portion of each said roll-retainingspring being less than two-thirds the mean circumference of said annularcavity, said roll-retaining springs being cooperatively connected tosaid roll cage by having said support legs of said springs caged in saidannular cavity in said roll cage.

4. A roller-type tube-expanding tool having a tapered mandrel, aplurality of expanding rolls, and a tubular roll cage with roll slotsformed therein, with said expanding rolls and said roll cage mountedabout said mandrel so that said rolls are radially movable in the rollslots in said roll cage and rotatable in and with said roll cage, aboutsaid mandrel; wherein a plurality of roll-retaining springs arecooperatively connected to said roll cage, said roll-retaining springsacting to radially retain said expanding rolls in said tool assembly,each of said roll-retaining springs being a formed wire having aU-shaped inger connected to two support legs, said linger being formedto lay on one of said rolls in said roll cage, said finger projectingangularly from the plane of said support legs, an annular cavity in saidroll cage, said annular cavity comprising an annular groove in theperiphery of said roll cage circumscribed by a band supported by theperipheral surface of said roll cage adjacent to said annular groove,said annular cavity being positioned in the shank portion of said rollcage to thereby be positioned outside the worlringlength portion of saidroll cage, said support legs, of said roll-retaining springs, beingformed to lay in said annular cavity in said roll cage, the overallcircular length of the support legs portion of each said roll-retainingspring being less than two-thirds the mean circumference of said annularcavity, said roll-retaining springs being cooperatively connected tosaid roll cage by having said support legs of said springs caged in saidannular cavity in said roll cage.

5. A tool as in claim 4; wherein at least some of said roll slots areangularly cock-ed so that said expanding rolls contained in said`angula-rly-coclred roll slots are cocked to effect a self-feedingaction of said mandrel.

6. A roill-retaining spring for a rollentype tube-expanding tool, saidtube-expanding tool having a tapered mandrel, a plurality of expandingrolls, and a tubular roll cage with roll slots formed therein, with saidexpanding rolls and said roll cage mounted about said mandrel so thatsaid rolls are radially movable in the roll slots in said roll cage androtatable in and with said roll cage, about said mandrel, saidroll-retaining spring being a formed Wire having a cl-shaped ngerconnected to two support legs, said linger being formed to lay on on@ ofsaid rolls in said roll cage, said linger projecting angularly from theplane .of said support legs, said roll cage having an annular cavity,said annular cavity cornprising an annular groove in the periphery ofsaid roll cage circumscribed by 'a band supported by the peripheralsurtace of said roll cage adjacent to said annular groove, said annularcavity being positioned in the shank portion of said roll cage tothereby be positioned outside the working-length portion of said rollcage, said support legs, of said roll-retaining spring, being formed tolay in said annular cavity in said roll cage, the overall circularlength of the support legs portion of said roll-retaining spring beingless than two-thirds the mean circumference of said annular cavity, saidrollretaining spring being cooperatively connectable to said roll cageby having said support legs ot said spring caged in said annular cavityin said roll `cage to thereby provide means for said roll-retainingspring to act radially to retain a said expanding roll in said toolassembly.

7. A roll cage for a roller-type tubeexpanding tool, said tube-expandingtool having a tapered mandrel, a plurality of expanding rolls, and saidroll cage, said roll cage being tubular with roll slots formed therein,said expanding rolls and said roll cage being mountable about saidmandrel with said rolls radially movable in the roll slots in said rollcage and rotatable in and with said roll cage, about said mandrel;wherein an annular groove in the peripheral surface of said roll cageprovides means for producing an `annular cavity in said roll cage, saidannular cavity being obtained by ycooperatively connecting acircurnscribing band supported by the peripheral surface of said rollcage adjacent to said annular groove, said annular groove beingpositioned in the shank portion of said roll cage to thereby positionsaid annular cavity in said shank portion of said roll cage to thusposition said annular cavity outside the Working length portion of saidroll cage, said `annular cavity providing means for cooperativelyconnecting a plurality of roll- `retaining springs, said roll-retainingsprings acting to radially retain said expanding rolls in said. toolassembly, each of said roll-retaining springs being a formed Wire havinga U-shaped iinger connected to two support legs, said linger beingformed to lay on one of said rolls in said roll cage, said iingerprojecting angularly from the plane of said support legs, said supportlegs being formed to lay in said annular cavity in said roll cage, theoverall circular length of the support legs portion of each saidrollaretaining spring being less than two-thirdsA the mean circumferenceof said annular cavity, a plurality of said roll-retaining springs beingcooperatively connectable to said roll cage by having said support legsof said springs caged in said annular cavity in said roll cage.

8. A roll cage as in claim 7; wherein at least some of said roll slotsare angularly cocked so that said expanding trolls contained in saidangularly-cocked roll slots are cocked to effect a self-feeding actionof said mandrel.

References Cited in the tile of this patent UNITED STATES PATENTS1,680,922 Wiedelie Aug. 14, 1928 2,543,007 Fitzgerald Feb. 27, 19512,575,591 Klaar Nov. 20, 1951 2,772,716 Stary Dec. 4, 1956

